Prof. Eiji Okada Profile

Prof. Eiji Okada

Professor at Keio Univ

SPIE Involvement:

Conference Program Committee | Author

Publications (63)

Proceedings Article | 20 September 2023 Paper

3D-printed head surface model of a standard brain template for scalp-cortex correlation of fNIRS

Tomohiro Kaneko, Eiji Okada

Proceedings Volume 12608, 126080I (2023) https://doi.org/10.1117/12.3007889

KEYWORDS: Head, 3D modeling, Brain, Natural surfaces, Geometrical optics, 3D imaging standards, Systems modeling, Standards development, Manufacturing, Brain tissue

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Proceedings Article | 9 August 2023 Paper

Monte Carlo modeling of photoacoustic guided technique in scattering media

Joya Arisu, Naoto Yamamura, Keiichi Nakagawa, Shu Takagi, Eiji Okada

Proceedings Volume 12628, 126281Z (2023) https://doi.org/10.1117/12.2670646

KEYWORDS: Refractive index, Anisotropy, Tissues, Monte Carlo methods, Geometrical optics, Photon transport, Photoacoustic spectroscopy, Scattering media, Light scattering, Waveguides

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Proceedings Article | 9 August 2023 Paper

Influence of the heterogeneity of extracerebral tissues on scalp-cortex correlation of fNIRS for infants

Rinka Tachikawa, Eiji Okada

Proceedings Volume 12628, 1262828 (2023) https://doi.org/10.1117/12.2670852

KEYWORDS: Tissues, Image segmentation, Skull, Head, Light scattering, Brain, Spatial resolution, Magnetic resonance imaging, Light absorption, Brain tissue

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SPIE Journal Paper | 31 May 2021 Open Access

Correlating functional near-infrared spectroscopy with underlying cortical regions of 0-, 1-, and 2-year-olds using theoretical light propagation analysis

Lin Cai, Eiji Okada, Yasuyo Minagawa, Hiroshi Kawaguchi

NPh, Vol. 8, Issue 02, 025009, (May 2021) https://doi.org/10.1117/12.10.1117/1.NPh.8.2.025009

KEYWORDS: Brain, Head, Near infrared spectroscopy, Optical properties, Geometrical optics, Tissues, Neurophotonics, Tissue optics, Magnetic resonance imaging, Skull

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Proceedings Article | 11 July 2019 Paper

Influence of optical path length on multi-wavelength measurement of oxy- and deoxy-hemoglobins in the skin

T. Shirai, E. Okada

Proceedings Volume 11074, 110742L (2019) https://doi.org/10.1117/12.2526898

KEYWORDS: Tissue optics, Skin, Geometrical optics, Reflectivity, Diffuse reflectance spectroscopy, Hemodynamics, Tissues, Absorption, Light wave propagation, Electronics

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Proceedings Article | 11 July 2019 Paper

Theoretical analysis of hemodynamic signal from the scalp in time-gated NIRS imaging using null source-detector separation

G. Nakamura, E. Okada

Proceedings Volume 11074, 110740S (2019) https://doi.org/10.1117/12.2526899

KEYWORDS: Signal detection, Near infrared spectroscopy, Hemodynamics, Absorption, Brain, Monte Carlo methods, Geometrical optics, Signal analyzers, Head, Neuroimaging

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Proceedings Article | 11 July 2019 Paper

Time-domain diffuse optical tomography with lp sparsity regularization for thyroid cancer imaging

Shinpei Okawa, Tetsuya Mimura, Hiroyuki Fujii, Hiroshi Kawaguchi, Yukari Tanikawa, Manabu Machida, Eiji Okada, Yoko Hoshi

Proceedings Volume 11074, 1107407 (2019) https://doi.org/10.1117/12.2526886

KEYWORDS: Image restoration, Cancer, Optical properties, Reconstruction algorithms, Algorithm development, Neck, Optical fibers, Diffuse optical tomography, Numerical simulations, Finite element methods

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Proceedings Article | 24 April 2018 Paper

Partial optical path length in the scalp in subject-specific head models for multi-distance probe configuration of near infrared spectroscopy

Taku Yanagisawa, Hiroshi Kawaguchi, Takayuki Obata, Eiji Okada

Proceedings Volume 10711, 107111J (2018) https://doi.org/10.1117/12.2319286

KEYWORDS: Geometrical optics, Head, Near infrared spectroscopy, Signal detection, Brain, Sensors, Blood, Monte Carlo methods, Electronics

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Proceedings Article | 24 April 2018 Paper

Measurement of head phantom by functional near infrared imaging using multi-distance probe configuration

Koki Hayabusa, Eiji Okada

Proceedings Volume 10711, 107111K (2018) https://doi.org/10.1117/12.2319282

KEYWORDS: Signal detection, Absorption, Head, Near infrared, Sensors, Blood, Brain, Neuroimaging

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Proceedings Article | 18 April 2017 Paper

Estimation of functional areas probed by near-infrared spectroscopy instruments

Tomonori Nitta, Ryohei Tsuyuki, Hiroshi Kawaguchi, Eiji Okada

Proceedings Volume 10251, 102511Z (2017) https://doi.org/10.1117/12.2275046

KEYWORDS: Head, Light scattering, Scattering, Tissue optics, Brain activation, Neuroimaging, Imaging spectroscopy, Image registration, Near infrared spectroscopy, Brain

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Proceedings Article | 18 April 2017 Paper

Light propagation analysis for fluorescence measurements of a molecular probe in the brain

Kota Asai, Takuya Togashi, Eiji Okada

Proceedings Volume 10251, 102511S (2017) https://doi.org/10.1117/12.2274896

KEYWORDS: Tissues, Brain, Luminescence, Geometrical optics, Tissue optics, Skull, Head, Natural surfaces, Monte Carlo methods, Molecular electronics, Alzheimer's disease, Light sources

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Proceedings Article | 10 March 2015 Paper

Numerical modeling of photon migration in the cerebral cortex of the living rat using the radiative transport equation

Hiroyuki Fujii, Shinpei Okawa, Ken Nadamoto, Eiji Okada, Yukio Yamada, Yoko Hoshi, Masao Watanabe

Proceedings Volume 9333, 933313 (2015) https://doi.org/10.1117/12.2079265

KEYWORDS: Cerebral cortex, Tissues, Optical properties, Scattering, Monte Carlo methods, Picosecond phenomena, Biomedical optics, Light scattering, Numerical modeling, Numerical analysis

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Proceedings Article | 14 June 2013 Paper

A hybrid MC-FEM model for analysis of light propagation in highly scattering medium

Kazuki Kurihara, Xue Wu, Eiji Okada, Hamid Dehghani

Proceedings Volume 8799, 87990E (2013) https://doi.org/10.1117/12.2032613

KEYWORDS: Photons, Finite element methods, Scattering, Light sources, Light scattering, Near infrared spectroscopy, Monte Carlo methods, Diffusion, Hemodynamics, Head

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Proceedings Article | 14 June 2013 Paper

Three-dimensional cortex model including vascular structure for estimation of path length for optical imaging

Takahiro Kikuchi, Hiroyuki Takuwa, Kazuto Masamoto, Hiroshi Ito, Eiji Okada

Proceedings Volume 8799, 87990M (2013) https://doi.org/10.1117/12.2032509

KEYWORDS: Blood vessels, Geometrical optics, Tissue optics, Tissues, 3D modeling, Sensors, 3D image processing, Optical imaging, Absorption, Two photon excitation microscopy

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Proceedings Article | 25 March 2013 Paper

Near-infrared spectroscopy system with non-contact source and detector for in vivo multi-distance measurement of deep biological tissue

Tsukasa Funane, Hirokazu Atsumori, Masashi Kiguchi, Yukari Tanikawa, Eiji Okada

Proceedings Volume 8578, 85782W (2013) https://doi.org/10.1117/12.2002254

KEYWORDS: Near infrared spectroscopy, Tissue optics, Optical scanning systems, Brain, Sensors, Neuroimaging, Skin, Light, In vivo imaging, Stray light

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SPIE Journal Paper | 5 April 2012 Open Access

Dynamic phantom with two stage-driven absorbers for mimicking hemoglobin changes in superficial and deep tissues

Tsukasa Funane, Hirokazu Atsumori, Masashi Kiguchi, Eiji Okada, Yukari Tanikawa

JBO, Vol. 17, Issue 04, 047001, (April 2012) https://doi.org/10.1117/12.10.1117/1.JBO.17.4.047001

KEYWORDS: Absorption, Tissues, Near infrared spectroscopy, Autoregressive models, Independent component analysis, Monte Carlo methods, Aluminum, Brain, Blood, Absorbance

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Proceedings Article | 9 July 2011 Paper

Analysis of the diffuse reflectance spectra of skin due to detection system

Shoji Takano, Eiji Okada

Proceedings Volume 8088, 80881A (2011) https://doi.org/10.1117/12.889241

KEYWORDS: Skin, Laser induced plasma spectroscopy, Diffuse reflectance spectroscopy, Integrating spheres, Absorption, Reflectivity, Monte Carlo methods, Optical properties, Photon transport, Scattering

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Proceedings Article | 17 June 2011 Paper

Evaluation of the position resolution of NIR topography by localised visual stimulation

Hirokazu Kakuta, Eiji Okada

Proceedings Volume 8088, 80881B (2011) https://doi.org/10.1117/12.889798

KEYWORDS: Brain activation, Visualization, Near infrared, Visual cortex, Inverse problems, Inverse optics, Brain, Image resolution, Visual optics, Optical resolution

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Proceedings Article | 17 June 2011 Paper

Segmentation of magnetic resonance images to construct human head model for diffuse optical imaging

Kazuki Kurihara, Hiroshi Kawaguchi, Yosuke Takahashi, Takayuki Obata, Eiji Okada

Proceedings Volume 8088, 80880J (2011) https://doi.org/10.1117/12.889813

KEYWORDS: Image segmentation, Magnetic resonance imaging, Head, Skull, Tissues, Magnetism, Brain, Diffuse optical imaging, Image processing algorithms and systems, Neuroimaging

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Proceedings Article | 15 June 2011 Paper

Phantom experiments for quantitative evaluation of topographic image by mapping algorithm

Yusuke Yoshida, Hirokazu Kakuta, Hiroshi Kawaguchi, Eiji Okada

Proceedings Volume 8088, 80881D (2011) https://doi.org/10.1117/12.889808

KEYWORDS: Brain activation, Absorption, Diamond, Head, Image analysis, Sensors, Brain mapping, Near infrared, Spatial resolution, Monte Carlo methods

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Proceedings Article | 15 June 2011 Paper

Comparison of temporal response to cerebral blood flow measured by laser speckle flowgraphy and laser Doppler flowmetry

Masashi Kusano, Haruka Nakayama, Hiroyuki Takuwa, Kazuto Masamoto, Iwao Kanno, Eiji Okada

Proceedings Volume 8088, 80880E (2011) https://doi.org/10.1117/12.889787

KEYWORDS: Speckle, Speckle pattern, Blood circulation, Doppler effect, CCD cameras, Cerebral blood flow, Temporal resolution, Blood vessels, Brain activation, Somatosensory cortex

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Proceedings Article | 10 July 2009 Paper

Influence of SNR on statistical analysis of spatial extent of brain activation measured by multi-spectral imaging

Naotaka Sakashita, Koichiro Sakaguchi, Satoshi Matsuo, Haruka Nakayama, Takushige Katsura, Kyoko Yamazaki, Naoki Tanaka, Hideo Kawaguchi, Atsushi Maki, Eiji Okada

Proceedings Volume 7369, 73690Z (2009) https://doi.org/10.1117/12.831688

KEYWORDS: Signal to noise ratio, Brain activation, Statistical analysis, Reflectivity, Brain mapping, Optical filters, Signal detection, Beam splitters, Tissue optics, Brain

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Proceedings Article | 10 July 2009 Paper

Measurements of temporal-spatial change in blood flow and volume in exposed cortex of guinea pig evoked by auditory stimulation

Haruka Nakayama, Koichiro Sakaguchi, Satoshi Matsuo, Naotaka Sakashita, Takushige Katsura, Kyoko Yamazaki, Naoki Tanaka, Hideo Kawaguchi, Atsushi Maki, Eiji Okada

Proceedings Volume 7369, 73691G (2009) https://doi.org/10.1117/12.831655

KEYWORDS: Blood circulation, Blood, Imaging systems, Speckle, Tissues, Reflectivity, Speckle pattern, Optical imaging, Brain activation, Laser speckle imaging

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Proceedings Article | 12 July 2007 Paper

Evaluation of image reconstruction algorithm for near infrared topography by virtual head phantom

Hiroshi Kawaguchi, Eiji Okada

Proceedings Volume 6629, 662906 (2007) https://doi.org/10.1117/12.728105

KEYWORDS: Head, Image restoration, Absorption, Reconstruction algorithms, Near infrared, Spatial resolution, Brain activation, Tissues, Sensors, Magnetic resonance imaging

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Proceedings Article | 12 July 2007 Paper

Modeling of influence of frontal sinus on NIRS signal of brain activation

Daisuke Yamamoto, Shoko Kuroda, Eiji Okada

Proceedings Volume 6629, 66290S (2007) https://doi.org/10.1117/12.728255

KEYWORDS: Geometrical optics, Head, Near infrared spectroscopy, Tissues, Brain activation, Skull, Tissue optics, Brain, Absorption, Scattering

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Proceedings Article | 12 July 2007 Paper

Path-length correction for the haemoglobin-concentration measurement using the skull cranial window by multi-spectral imaging analysis

Koichiro Sakaguchi, Shunsuke Furukawa, Takushige Katsura, Kyoko Yamazaki, Hideo Kawaguchi, Atsushi Maki, Eiji Okada

Proceedings Volume 6629, 66290K (2007) https://doi.org/10.1117/12.728225

KEYWORDS: Skull, Tissue optics, Reflectivity, Tissues, Cranial windows, Monte Carlo methods, Brain, Brain activation, Neuroimaging, Geometrical optics

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Proceedings Article | 27 October 2006 Paper

Theoretical analysis of crosstalk in near-infrared topography

E. Okada, N. Okui

Proceedings Volume 6047, 60470V (2006) https://doi.org/10.1117/12.710677

KEYWORDS: Absorption, Brain, Tissue optics, Sensors, Near infrared, Monte Carlo methods, Geometrical optics, Head, Skull, Neuroimaging

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Proceedings Article | 26 October 2005 Paper

Image reconstruction using spatial sensitivity profile with the constraint of spatial frequency in image for near-infrared topography

Hiroshi Kawaguchi, Eiji Okada

Proceedings Volume 5859, 585915 (2005) https://doi.org/10.1117/12.632871

KEYWORDS: Image restoration, Absorption, Reconstruction algorithms, Spatial resolution, Inverse problems, Linear filtering, Head, Spatial frequencies, Near infrared, Sensors

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Proceedings Article | 8 October 2005 Paper

Estimation of path length factor for measurement of haemoglobin concentration in the exposed cortical tissue

K. Sakaguchi, T. Tachibana, K. Yokoyama, S. Furukawa, T. Katsura, A. Maki, H. Kawaguchi, E. Okada

Proceedings Volume 5859, 58590S (2005) https://doi.org/10.1117/12.632848

KEYWORDS: Tissue optics, Reflectivity, Tissues, Monte Carlo methods, Geometrical optics, Brain, Optical properties, Imaging systems, Neuroimaging, CCD cameras

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Proceedings Article | 8 October 2005 Paper

Crosstalk in the measurement of focal brain activation by near-infrared topography

N. Okui, E. Okada

Proceedings Volume 5859, 58591A (2005) https://doi.org/10.1117/12.632876

KEYWORDS: Absorption, Tissue optics, Monte Carlo methods, Skull, Brain activation, Head, Geometrical optics, Near infrared, Light, Brain

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SPIE Journal Paper | 1 January 2005 Open Access

Wavelength dependence of crosstalk in dual-wavelength measurement of oxy- and deoxy-hemoglobin

Nobuhiro Okui, Eiji Okada

JBO, Vol. 10, Issue 01, 011015, (January 2005) https://doi.org/10.1117/12.10.1117/1.1846076

KEYWORDS: Tissue optics, Skull, Geometrical optics, Near infrared spectroscopy, Monte Carlo methods, Head, Tissues, Optical properties, Absorption, Phase measurement

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SPIE Journal Paper | 1 January 2005 Open Access

Interpretation of principal components of the reflectance spectra obtained from multispectral images of exposed pig brain

Kentaro Yokoyama, Motoshi Watanabe, Yohei Watanabe, Eiji Okada

JBO, Vol. 10, Issue 01, 011005, (January 2005) https://doi.org/10.1117/12.10.1117/1.1854671

KEYWORDS: Reflectivity, Tissue optics, Multispectral imaging, Absorption, Tissues, Geometrical optics, Monte Carlo methods, Principal component analysis, Brain, Photons

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Proceedings Article | 29 July 2004 Paper

Modeling of light distribution in the brain for topographical imaging

Eiji Okada, Toshiyuki Hayashi, Hiroshi Kawaguchi

Proceedings Volume 5486, (2004) https://doi.org/10.1117/12.571349

KEYWORDS: Absorption, Brain, Head, Neuroimaging, Sensors, Reconstruction algorithms, Spatial resolution, Scattering, Monte Carlo methods, Light scattering

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